Telephone-exchange system



. W. P. ANDRICK AND J. F. DAHL.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED OCT. 25. i920 Wye/7mm: Wa/hce F. A fldH'c/r Jae/r F 061/7/ by A7734 UNITED STATES PATENT OFFICE.

WALLACE I. ANDRICK, OF IIOHOKUS, AND JACK F.DAHL, OF EAST ORANGE, NEW

JERSEY, ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF

NEW YORK, N. Y., A. CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Application filed October 25, 1920. Serial No. 419,413.

To all whom it may concern:

Be it known that we, WALLACE P. AN- DRICK and JACK F. DAHL, citizens of the United States, residing at Hohokus, in the county of Bergen, State of New Jersey, and at East Orange, in the county of Essex, State of New Jersey, respectively, have invented certain new and useful Improvements in Telephone-Exchange Systems, of

which the following is a full, clear, concise, and exact description.

This invention relates .to telephone exchange systems and more particular 1y to those having certain groups of subscribers whom it is desirable to call and converse with simultaneously.

It is frequently very desirable that a certain special group of telephone subscribers be called with minimum delay so that some very important information of common interest may be transmitted. An example of this is the case where it is necessary to call the members of a volunteer fire department and impart to them information concerning the location of a fire.

Under such circumstances it is, of course, very important that the information be given with the least possible delayand it is evident that a circuit arrangement by which all subscribers of the group may be called at one time without the necessity of establishing individual connections as ordinarily, is fundamentally the best method of accomplishing this.

It is the object of this invention to provide an improved and inexpensive method of accomplishing the foregoing result.

To attain this object in accordance with a feature of this invention, the regular cutoff relay of the line, which is re ularly actuated in response to the insertlon of the plug of the operators link circuit into the line jack, is also actuated upon the operation of the means for connecting together the associated lines. 1

Another feature of the invention is the provision of means by which particular lines in the central office may be readily grouped, so as to allow common ringing and talking without disturbing the regular circuits used for individual connections.

These and other features not specificall mentioned will clearly appear from the f0 lowing specification andthe accompanying drawing in which the figure shows one embodiment of the invention as applied to a common battery telephone office in which are, used terminaljacks having three contacts. Subscribers? lines 'A, B, C and D are shown terminating on jacks 1, 2, 3 and 4, respectively, with which are associated grouping relays 5 and 6, the function of which is to group the lines to other for common talking and ringing. L is a line of a calling subscriber who is answered by an operator in control of a plurality of link circuits L, which conform to the usual repeating coil, common battery type, and which are not a part of this invention.

With these link circuits is associated an operators telephone circuit T which is adapted" for use in connection with the establishment of a regular individual connection with a line, A, B, C or D, when a key 8 is in the normal position-as shown. WVhen key 8 is in the operated position, telephone circuit T is then adapted for use with the common connection. The subscribers of lines .A, B, C and D are called by the actuation of a key 9. In addition to the grouping relays 5 and 6, a relay 7 is also shown. When it is desired to increase the number of lines in the associated special service group, the winding of relay 7 may be connected to a common conductor 43,and the leads from the contacts to the proper terminals (not shown) of the lines to be connected. Similarly, other relays (not shown) may be connected to extend the special service. i

It is thought that the invention will be more fullly comprehended by the following description of the operation of the system illustrated by the drawing.

The subscriber'of the line E desire to converse with the subscriber of line A signals the operator in the usual manner by removing the receiver from the hook, operating thereby line relay 10 and causing the illumination of line lamp 11. The operator in control of link circuit L then responds by inserting plug 12 into jack 13, operating cut-off relay 14 over the sleeve circuit of plug 12 and jack 13, causing the release of relay 10 and the extinguishing of lamp 11. To call the subscriber of line A, plug 15 is inserted into jack 1, operating cut-off relay 16 associated with line A. Upon who may the actuation of ringing key 17, the telephone bell of subscribers line A will be rung in the usual manner and, upon the subscribers responding by the removal of the receiver from the switchhook, a conversational connection will be established over an obvious path. It is thought unnecessary to trace in detail the various circuits of this particular connection, inasmuch as they are well known in the art and do not form a part of this invention. They are shown only to make the description more complete and to illustrate the working of this system as a whole.

The preceding covers the establishment of. a regular individual connection. Assume now that the subscriber of line E wishes to report a fire or to convey to a certain selected group of subscribers some important information with the minimum possible de lay; To do this the operator in control of link circuit L is signaled in the usual manner, and responds by inserting plug 12 into jack 13. Ascertaining the details of the information which it is desired to transmit to the special group of subscribers, the operator does not, as in the case of an ordinary individual connection, insert the calling plug into a jack, but actuates key 8, causing the actuation of relays 44 and 42 over obvious circuits. The actuation of relay 42 causes the operation of relays 5 and 6 over obvious circuits established from battery through the contact of relay 42. The actuation of relay 5 causes ground to be connected to the tip conductor of subscribers line A at the upper outside contact of relay 5 1andground to the tipconductor of subsc'ribers line B at the lower inside contact of'relay 5. Corresponding contacts of relay 6 upon its actuation, also connect ground to the tip conductors of subscribers" lines C and D. The upper middle and the lower middle contacts of relay 5 and the upper middle and the lower middle contacts of relay 6 connect the common conductor 18 through resistances 19, 20, 21, and 22, respectively to the ring conductors of subscribers lines A, B, C, and D. By the actuation of relays 5 and 6, the cut-off relays 16, 23, 24 and 25 are actuated over circuits established from battery, through the resistances 26, 27, 28 and 29, the associated con tacts on relays 5 and 6 and the windings of the corresponding cut-off relays to ground. The actuation of the cut-off relays disconnects. at their respective contacts, the line relays 30, 31, 32 and 33. The operator now rings on the grouped lines A, B, C and D by actuation of the ringing key 9. The" path of ringing current for the subscribers line A will be traced and will suflice to explain the exactly similar paths of the current through the other lines. The ringing circuit extends from source of grounded ringing current 34, alternate contact of key 9, common conductor 18, resistance 19, upper middle contact of relay 5, ring conductor of subscribers line A, telephone bell of line A, and tip conductor to ground at the upper contact of relay 5. After each subscriber on the called lines has responded, current from the battery, associated with telephone circuit T, will be supplied to each of the transmitters of thetelephones of subscribers lines A, B, C and D. It will be sufiicient to trace the circuit of a single line, that of subscribers line A, from battery through battery 35, upper and lower windings of induction coil 36 in series through the normal contact of key 9, common conductor 18, resistance 19, upper middle contact of relay 5, ring conductor of subscribers line A, telephone sub-set of line A, tip conductor of this line to ground at the upper contact of relay'5.

Resistance 19, 20, 21 and 22 through which ringing and talking current is supplied to the associated lines perform the useful function of effecting an approximate equalization of current flow, regardless of the electrical condition of the lines. .For a common ringing and talking system this is very (lesirable since a short circuit or ground on one or more lines, might shunt away sufiicient current to render impossible the proper functioning of all lines of the associated group. The resistance in the circuit of each line obviates this difiiculty. Resistances 26, 27 28 and 29 are used in series with the windings of cut-off relays 16, 23, 24 and 25, to limit the current in the windings to that obtained-on a regular individual line connection, when plug 15 is inserted into one of the line jacks. Under this condition each of the lines A, B, G and D will test busy on a common connection, when the tip of the plug 15 touches the sleeve of the corresponding jacks, with the same volume of click as on an individual connection. actuated key 8, the lower left-hand windfng of induction coil 37 was disconnected from the circuit of transmitter 38 at the normal right-hand contact of key 8, and the actuation of relay 44 connected transmitter 38 in series with the lower winding of induction coil 36 and permitted current to flow from battery 35 over the following path: battery 35, lower alternate contact of relay 44, transmitter 38, middle alternate contact of relay 44, normal contact of key 39, lower winding of induction coil 36, to battery 35. The actuation of relay 44 also connected receiver 40 into the following associated circuit: from right-hand terminal of the upper winding of induction coil 36, upper alternate contact of relay 44, receiver 40, condenser 41, lower alternate contact of relay 44, transmitter 38, middle alternate contact of relay 44, contact of key 39, to left-hand terminal of the upper winding of induction coil 36. This operation places the receiver in a cir- \Vhen the opterator 1 cuit, the terminals of which are connected to the terminals of transmitter 38. The operators telephone is now in conversational connection with the subscribers of lines A, B, C and D. In order to improve the receiving efiiciency of the circuit, key 39 may be actuated, when the operator is listening, which discontinues the current from battery 35, through the transmitter 38. After the information has been conveyed to the subscribers of lines A, B, C and D, the operator restores the key 8 to normal, releasing relays 44 and 42. The release of relay 42 causes the release of relays 5, 6 and 7 All apparatus is now restored to normal and each vof the lines of the associated subscribers is again free to receive an individual call.

What is claimed is:

l. In a telephone exchange system, a group of associated telephone lines,line signaling means individual to each of said lines to signal the central oflice, a telephone c1rcuit common to the group, a resistance associated with each line of the group, a source of current associated with the common telephone, means for connecting together for common talking the associated lines, said resistance approximately equalizing the current flow from said source to the lines irrespective of their electrical condition, and means responsive upon the connecting together of the associated lines to disconnect each line signaling means from its associated line.

2. In a telephone exchange system, a group of associated telephone lines, a telephone circuit commonto the group, said telephone circuit including an impedance device, a'source oftransmitter current, a grouping circuit to connect for common talkmg and ringing the corresponding conductors of each line, and means for supplying through the impedance device, ofsaid telephone circuit transmitter current from said source to the telephonelinesof said group.

3. In a telephone exchange system, a group of associated telephone lines, a telephone line of a calling subscriber, an operators telephone, means for connecting said operators telephone in conversational relation with the line of said calling subscriber, means for connecting for common talking and ringing said lassociated telephone lines,

connection, terminals a source of current, means for changing the normal circuit connection of the operators telephone to furnish transmitter current from said source to the associated lines, means for ringing simultaneously the grouped lines, said means being controlled by the changing of connections of the operators telephone for the common conversation, and means for connecting said operators telephone in conversational relation with the grouped lines.

4. In a telephone exchange system, a group of associated common battery telephone lines, an operators telephone circuit with impedance coils for common conversation with said telephone lines, a source of current, means for supplying to the associated lines transmitter current source through the impedance coils, and means for utilizing the'inductance characteristics of the impedance coils of the said telephone circuit in connection with the supply of current to the associated lines.

5. In a manual telephone exchange system, a group of associated common battery telephone lines normally adapted for i'ndividual for said lines having test contacts, an operators telephone circuit," means for grouping the lines together with said operators telephone circuit for commontalking and ringing, and means for maintaining the test contacts of the terminals at essentially the same potential for both common and individual connections.

6. In a telephone exchan group of associated telephone ines, line signaling means individual to each of said lines to signal the central ofiice, a resistance associated witheach line of the group, a source of ringing current, means for connecting together for common ringing the associated lines, said resistance approximately equalizing the current .flow from said source 0 each line irrespective of its electrical condition, and means responsive upon the connecting together of the associated lines to disconnect each line signaling means from its associated line.

In witness whereof, we hereunto subscribe our names this 19th day of October A. D., 1920.

' WALLACE P. ANDRICK. JACK F. DAHL.

from said e system, a 

